Aiichiro Nitori begins his journey as a first-year student at Samezuka Academy, progressing to third-year before attending Shimogami University. Born January 4th under the Capricorn sign, he stands 168 cm tall initially, later growing to 171 cm. He possesses gray hair, blue eyes, and a distinct teardrop-shaped mole diagonally beneath his right eye. His image color is light blue, and his motif animal is the duck. His swimming path was ignited in elementary school, participating in the same competition as Rin Matsuoka, Haruka Nanase, Makoto Tachibana, and Nagisa Hazuki. Witnessing Rin's relay after his own team's preliminary loss sparked profound admiration, shaping his dedication to competitive swimming. He aspires to emulate Rin's versatility, initially focusing on long-distance freestyle before rigorously training in breaststroke to qualify for relay events alongside Rin. Early setbacks, like exclusion from the prefectural relay, were overcome through persistent training guided by Sosuke Yamazaki, leading to personal bests and a relay spot in regional competitions. Friendly and talkative, Nitori sometimes makes inadvertent remarks yet remains undeterred by Rin's stern reactions. He demonstrates unwavering perseverance and earnestness in club activities, capable of firm professionalism like enforcing swim attire rules. Contrasting this diligence, his room is frequently untidy. He maintains unique habits, preserving his umbilical cord and childhood journals. His hobbies include reading and playing with his pet dog. He favors borscht and sandwiches but dislikes sour foods like pickled plums. Relationships are central to his growth. He rooms with Rin in his first year, later sharing with Momotaro Mikoshiba in his second year. Rin initially addresses him formally but eventually adopts the nickname "Ai," signaling growing camaraderie. Nitori views Rin as a role model, aspiring to swim beside him and experiencing distress when unable to comprehend Rin's choices. Post-high school, he attends Shimogami University alongside Rei Ryugazaki. His uncle, Mikhail Makarovich Nitori, serves as Rin's coach in Australia. His leadership evolves when Rin appoints him captain of Samezuka's swim team upon graduation. In this role, he mentors newcomers like Momotaro Mikoshiba and leads the team through national tournaments, including a breaststroke victory over Nagisa Hazuki during qualifying rounds. His tenure marks a transition from eager underclassman to responsible leader committed to the team's legacy. Health considerations include implied asthma, evidenced by an inhaler in his desk and wheezing during strenuous activities.